Perplexed by today's turbulent American political scene? Not to worry: A distinguished political scientist wrote an essay 26 years ago that anticipated our predicament with eerie explanatory power. The only downside is that its author specialized in the causes of democratic collapse.

"The Perils of Presidentialism," by Yale University's Juan J. Linz, compared the Westminster-style parliamentary system with "presidentialist" systems that divide executive and legislative power between separately elected presidents and assemblies. The former, he concluded, were inherently more stable than the latter.

This was an unlikely argument for an academic in the United States - a presidentialist nation deeply attached to separation of powers as a constitutional principle and equally confident of its political stability.

Yet Linz, a Spaniard, had closely studied his native country's 20th-century journey from democracy to dictatorship and back again, as well as the chronically unstable presidential systems of Spain's former colonies in Latin America.

Drawing on that history, Linz identified comparative disadvantages of "presidentialist" democracy. The fundamental one: Whereas a prime minister owes his power to the same majority that produces parliament, the president and legislature in a presidentialist democracy can both claim to represent the national majority, a source of competition that can spawn conflict, even chaos, when rival parties control the two branches.

Presidential systems include a fixed term for the chief executive, to add predictability and to curb dictatorial tendencies. However, this intended stabilizer actually makes politics "rigid," Linz warned. Whereas a parliamentary system can oust or, alternatively, fortify, controversial prime ministers through a vote of confidence, the only way to get rid of a wayward president before his term ends is by risking an impeachment crisis.

The rise and fall of prime ministers might give parliamentary countries such as Italy and Japan an almost comic appearance of political instability; but, Linz cleverly argued, their revolving door is actually a source of stability, since short-term kerfuffles help "avoid deeper crises." Governments come and go; democracy remains.

In contrast, the fixed presidential term adds a "winner take all" element to presidential elections, since parties and voters know that they're likely to be stuck with the victor for years. This "raises the stakes in presidential elections and inevitably exacerbates their attendant tension and polarization," Linz wrote, as if reporting from New Hampshire on Tuesday.

Adding to the drama, presidentialism makes the chief executive a personal repository "for whatever exaggerated expectations his supporters may harbor. They are prone to think that he has more power than he really has or should have." For his part, a president may "tend to conflate his supporters with 'the people' as a whole," making the "obstacles and opposition he encounters seem particularly annoying."

Americans have seen this dynamic at work in such episodes as Franklin D. Roosevelt's attempted "packing" of the Supreme Court and President Obama's use of executive action to counter Republican naysaying on guns, immigration and other issues.

Among Latin American failures of presidentialism, perhaps the most dramatic was the overthrow of Chilean President Salvador Allende in a 1973 military coup, after he tried and failed to swing his nation sharply left against center-right opposition, in parliament and in the streets.

For Linz, who died in 2013, such cases established a rule: Presidentialist democracy is most vulnerable in a polarized society with multiple parties and a volatile electorate.

Accordingly, he saw the United States' system as a stable exception because most voters were middle-class centrists and its two parties differed only "within a larger, moderate consensus."

This assessment seemed plausible when Linz wrote it in 1990. Nevertheless, he failed to address the growing polarization and political crisis that led to the Civil War in 1861, the proximate cause of which was Southern panic at what Abraham Lincoln would do with presidential power after the "winner take all" election of 1860.

When you consider that precedent, Linz's argument for exceptionally stable American presidentialism gets ever so slightly less reassuring.

In the quarter-century since he published his essay, the centrist Cold War-era political consensus has broken down. Decaying, too, are the two ideologically flexible "big tent" party coalitions that subscribed to that consensus.

Rank-and-file Democrats and Republicans are polarizing along ideological lines while further sorting themselves into subgroups ominously correlated with race, region and identity.

Long-standing establishments in both parties risk losing control to men - Donald Trump for the GOP, Bernie Sanders for the Democrats - whose first major acts of party membership were to launch insurgent presidential nomination bids.

The intense following each arouses recalls Linz's concerns about "the interaction between a popular president and the crowd acclaiming him," which "can generate fear among his opponents and a tense political climate."

By contrast, establishment politicians are wishy-washy, thoroughly compromised if not corrupt and, perhaps worst of all, boring. We may miss them someday.